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Publication numberUS20060211925 A1
Publication typeApplication
Application numberUS 11/367,034
Publication dateSep 21, 2006
Filing dateMar 1, 2006
Priority dateMar 1, 2005
Also published asDE602006014538D1, EP1860989A1, EP1860990A1, EP1860991A1, EP1860992A1, EP1860993A1, EP1860994A1, EP1860995A1, EP1860996A1, EP1860997A1, EP1863380A2, EP1895892A1, EP1895892B1, EP2228005A1, EP2286721A2, EP2286721A3, EP2305104A2, EP2305104A3, US7377794, US7563110, US7596398, US7647083, US7729733, US7761127, US7764982, US7957780, US8050728, US8130105, US8190223, US8224411, US8255027, US8301217, US8385996, US8483787, US8560032, US8581732, US8626255, US8634889, US8718735, US8849365, US8912909, US8929964, US9131882, US9167995, US9241662, US9351675, US20060211922, US20060211923, US20060211924, US20060211932, US20060220881, US20060226992, US20060229509, US20060238358, US20060241358, US20060241363, US20080220633, US20100022859, US20100049020, US20100228108, US20110009719, US20110237914, US20120046530, US20120161970, US20120232359, US20120232363, US20130172701, US20130317327, US20140142399, US20140142402, US20140194709, US20140309506, US20150087938, US20150133755, US20160073967, WO2006094107A1, WO2006094108A1, WO2006094109A1, WO2006094155A1, WO2006094168A1, WO2006094169A1, WO2006094170A1, WO2006094171A1, WO2006094279A1, WO2006115580A2, WO2006115580A3, WO2006118654A1
Publication number11367034, 367034, US 2006/0211925 A1, US 2006/211925 A1, US 20060211925 A1, US 20060211925A1, US 2006211925 A1, US 2006211925A1, US-A1-20060211925, US-A1-2006211925, US2006/0211925A1, US2006/211925A1, US20060211925 A1, US20060211925A1, US2006211925 A1, US2006211925A1
InventorsMarcelo Lamego, Mohamed Diab, Ammar Al-Ali
Original AssigneeMarcelo Lamego, Mohamed Diab, Ammar Al-Ali
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Physiological parameter confidence measure
US 20060211925 A1
Abstract
Confidence in a physiological parameter is measured from physiological data responsive to the intensity of multiple wavelengths of optical radiation after tissue attenuation. The physiological parameter is estimated based upon the physiological data. Reference data clusters are stored according to known values of the physiological parameter. At least one of the data clusters is selected according to the estimated physiological parameter. The confidence measure is determined from a comparison of the selected data clusters and the physiological data.
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Claims(23)
1. A method of determining a measure of confidence in a physiological parameter, the physiological parameter determined by transmitting multiple wavelengths of optical radiation into a tissue site and detecting the optical radiation after tissue attenuation, the method comprising:
deriving physiological data responsive to the intensity of multiple wavelengths of optical radiation transmitted into a tissue site and detected after tissue attenuation;
estimating a physiological parameter based upon the physiological data;
providing a physiological data reference;
obtaining at least one data cluster from the physiological data reference; and
determining a measure of confidence in the estimated physiological parameter based upon the at least one data cluster and the derived physiological data.
2. The method according to claim 1 wherein the providing step comprises:
predetermining the physiological data for known values of the physiological parameter across a sample population;
clustering the data according to the physiological parameter values; and
storing the data clusters so as to be retrievable according to the physiological parameter values.
3. The method according to claim 2 wherein the obtaining step comprises selecting the at least one data cluster according to the estimated physiological parameter.
4. The method according to claim 3 wherein the selecting step comprises:
determining at least one data cluster having a corresponding physiological parameter value closest to the estimated physiological parameter; and
reading the determined at least one data cluster from the memory.
5. The method according to claim 4 wherein the physiological data are ratios of normalized plethysmographs (NP ratios).
6. The method according to claim 5 wherein the physiological parameter is at least one of SpO2, MetHb and HbCO.
7. The method according to claim 6 wherein the data clusters are a plurality of parameteric curves of NP ratio versus wavelength.
8. The method according to claim 6 wherein the data clusters are probability distributions of NP ratios.
9. A physiological parameter confidence measurement method comprising:
deriving physiological data responsive to the intensity of multiple wavelengths of optical radiation transmitted into a tissue site and detected after tissue attenuation;
estimating a physiological parameter based upon the physiological data;
providing a physiological data reference having a plurality of data clusters each corresponding to a particular value of the physiological parameter,;
comparing at least one of the data clusters to the physiological data; and
indicating confidence in the estimated physiological parameter based upon the comparison.
10. The physiological parameter confidence measurement method according to claim 9 further comprising associating a probability function with each of the data clusters.
11. The physiological parameter confidence measurement method according to claim 10 wherein the comparing step comprises determining a probability that the derived physiological data corresponds to the estimated physiological parameter.
12. The physiological parameter confidence measurement method according to claim 11 wherein the indicating step comprises generating at least one of a visual indication and an audible indication corresponding to the determined probability.
13. The physiological parameter confidence measurement method according to claim 12 further comprising triggering an alarm that a probe-off condition exists when the determined probability is below a predetermined threshold.
14. A confidence measurement system comprising:
a plurality of physiological data responsive to the intensity of multiple wavelengths of optical radiation transmitted into a tissue site and detected after tissue attenuation;
a parameter estimator configured to input the physiological data and output an estimate of a physiological parameter;
a physiological data reference having a plurality of data clusters corresponding to known values of the physiological parameter; and
a confidence measurer adapted to compare the physiological data with the data clusters so as to calculate a measure of confidence in the physiological parameter estimate.
15. The confidence measurement system according to claim 14 wherein the physiological data comprises a plurality of ratios of normalized plethysmographs corresponding to the multiple wavelengths of optical radiation.
16. The confidence measurement system according to claim 15 wherein the parameter estimator comprises a value calculation corresponding to at least one of SpO2, HbCO, HbMet, Hbt, fractional oxygen saturation, bilirubin and glucose.
17. The confidence measurement system according to claim 16 wherein the physiological data reference comprises a plurality of known values of the physiological parameter, corresponding predetermined values of ratios of normalized plethysmographs and probabilities associated with the predetermined values.
18. The confidence measurement system according to claim 17 wherein the confidence measurer comprises a probability calculation that the input physiological data corresponds to the estimated physiological parameter.
19. The confidence measurement system according to claim 18 further comprising a confidence indicator responsive to the probability calculation.
20. The confidence measurement system according to claim 19 further comprising a probe-off indicator responsive to the probability calculation and a predetermined probability threshold.
21. A confidence measurement system comprising:
a plurality of physiological data responsive to the intensity of multiple wavelengths of optical radiation transmitted into a tissue site and detected after tissue attenuation;
a parameter estimator configured to input the physiological data and output a corresponding physiological parameter estimate;
a physiological data reference means for providing data clusters according to known values of the physiological parameter; and
a confidence measurement means for determining confidence in physiological parameter estimate based upon the physiological data and the data clusters.
22. The confidence measurement system according to claim 21 further comprising an output means for indicating confidence in the physiological parameter estimate.
23. The confidence measurement system according to claim 21 further comprising an alarm means for indicating a probe-off condition in response to low confidence in the physiological parameter estimate.
Description
    PRIORITY CLAIM TO RELATED PROVISIONAL APPLICATIONS
  • [0001]
    The present application claims priority benefit under 35 U.S.C. 119(e) to U.S. Provisional Patent Application Ser. No. 60/657,596, filed Mar. 1, 2005, entitled “Multiple Wavelength Sensor,” No. 60/657,281, filed Mar. 1, 2005, entitled “Physiological Parameter Confidence Measure,” No. 60/657,268, filed Mar. 1, 2005, entitled “Configurable Physiological Measurement System,” and No. 60/657,759, filed Mar. 1, 2005, entitled “Noninvasive Multi-Parameter Patient Monitor.” The present application incorporates the foregoing disclosures herein by reference.
  • CORPORATION BY REFERENCE OF COPENDING RELATED APPLICATIONS
  • [0002]
    The present application is related to the following copending U.S. utility applications:
    App. Sr. No. Filing Date Title Atty Dock.
    1 11/###,### Mar. 1, 2006 Multiple Wavelength MLR.002A
    Sensor Emitters
    2 11/###,### Mar. 1, 2006 Multiple Wavelength MLR.003A
    Sensor Equalization
    3 11/###,### Mar. 1, 2006 Multiple Wavelength MLR.004A
    Sensor Substrate
    4 11/###,### Mar. 1, 2006 Multiple Wavelength MLR.005A
    Sensor Interconnect
    5 11/###,### Mar. 1, 2006 Multiple Wavelength MLR.006A
    Sensor Attachment
    6 11/###,### Mar. 1, 2006 Multiple Wavelength MLR.009A
    Sensor Drivers
    7 11/###,### Mar. 1, 2006 Physiological Parameter MLR.010A
    Confidence Measure
    8 11/###,### Mar. 1, 2006 Configurable MLR.011A
    Physiological
    Measurement System
    9 11/###,### Mar. 1, 2006 Noninvasive Multi- MLR.012A
    Parameter Patient
    Monitor
    10 11/###,### Mar. 1, 2006 Noninvasive Multi- MLR.013A
    Parameter Patient
    Monitor
    11 11/###,### Mar. 1, 2006 Noninvasive Multi- MLR.014A
    Parameter Patient
    Monitor

    The present application incorporates the foregoing disclosures herein by reference.
  • BACKGROUND OF THE INVENTION
  • [0003]
    Spectroscopy is a common technique for measuring the concentration of organic and some inorganic constituents of a solution. The theoretical basis of this technique is the Beer-Lambert law, which states that the concentration ci of an absorbent in solution can be determined by the intensity of light transmitted through the solution, knowing the pathlength dλ, the intensity of the incident light I0,λ, and the extinction coefficient εi,λ at a particular wavelength λ. In generalized form, the Beer-Lambert law is expressed as: I λ = I 0 , λ - d λ μ a , λ ( 1 ) μ a , λ = i = 1 n ɛ i , λ c i ( 2 )
    where μα,λ is the bulk absorption coefficient and represents the probability of absorption per unit length. The minimum number of discrete wavelengths that are required to solve EQS. 1-2 are the number of significant absorbers that are present in the solution.
  • [0004]
    A practical application of this technique is pulse oximetry, which utilizes a noninvasive sensor to measure oxygen saturation (SpO2) and pulse rate. In general, the sensor has light emitting diodes (LEDs) that transmit optical radiation of red and infrared wavelengths into a tissue site and a detector that responds to the intensity of the optical radiation after absorption (e.g., by transmission or transreflectance) by pulsatile arterial blood flowing within the tissue site. Based on this response, a processor determines measurements for SpO2, pulse rate, and can output representative plethysmographic waveforms. Thus, “pulse oximetry” as used herein encompasses its broad ordinary meaning known to one of skill in the art, which includes at least those noninvasive procedures for measuring parameters of circulating blood through spectroscopy. Moreover, “plethysmograph” as used herein (commonly referred to as “photoplethysmograph”), encompasses its broad ordinary meaning known to one of skill in the art, which includes at least data representative of a change in the absorption of particular wavelengths of light as a function of the changes in body tissue resulting from pulsing blood.
  • [0005]
    Pulse oximeters capable of reading through motion induced noise are available from Masimo Corporation (“Masimo”) of Irvine, Calif. Moreover, portable and other oximeters capable of reading through motion induced noise are disclosed in at least U.S. Pat. Nos. 6,770,028, 6,658,276, 6,157,850, 6,002,952 5,769,785, and 5,758,644, which are owned by Masimo and are incorporated by reference herein. Such reading through motion oximeters have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care and neonatal units, general wards, home care, physical training, and virtually all types of monitoring scenarios.
  • [0006]
    FIG. 1 illustrates HbO2 and Hb absorption μα versus wavelength. At red and near IR wavelengths below 970 nm, where water has a significant peak, Hb and HbO2 are the only significant absorbers normally present in the blood. Thus, typically only two wavelengths are needed to resolve the concentrations of Hb and HbO2, e.g. a red (RD) wavelength at 660 nm and an infrared (IR) wavelength at 940 nm. In particular, SpO2 is computed based upon a red ratio RedAC/RedDC and an IR ratio IRAC/IRDC, which are the AC detector response magnitude at a particular wavelength normalized by the DC detector response at that wavelength. The normalization by the DC detector response reduces measurement sensitivity to variations in tissue thickness, emitter intensity and detector sensitivity, for example. The AC detector response is a plethysmograph, as described above. Thus, the red and IR ratios can be denoted as NPRD and NPIR respectively, where NP stands for “normalized plethysmograph.” In pulse oximetry, oxygen saturation is calculated from the ratio NPRD/NPIR.
  • SUMMARY OF THE INVENTION
  • [0007]
    A multiple wavelength sensor and a noninvasive multi-parameter patient monitor, such as referenced above, make blood absorption measurements at more than a red wavelength and an IR wavelength. In one embodiment, described below, blood absorption measurements are made at eight wavelengths. Advantageously, this rich wavelength data, compared with conventional pulse oximetry, allows a determination of a tissue profile or tissue characterization over a wavelength spectrum.
  • [0008]
    FIG. 2 illustrates an example of a “tissue profile” 200 for SpO2=97%. For this example, including FIGS. 3-4, below, the sensor emits eight wavelengths (610, 620, 630, 655, 700, 720, 800 and 905 nm). The graph is a plot of NP ratios 210 versus wavelength 220, where the NP ratios are of the form NPλ1/NPλ2. This is a generalization to multiple wavelengths of the ratio NPRD/NPIR described above for two (red and IR) wavelengths. In order to provide a common scale for these NP ratios, the ratios are calculated with respect to a reference wavelength, λr, which may be any of the available wavelengths. Thus, the plotted NP ratios are denoted NPλn/NPλr over the n available wavelengths, including λr. Note that the NP ratio at the reference wavelength is NPλr/NPλr=1, which is 800 nm in FIG. 2.
  • [0009]
    As shown in FIG. 2, when a sensor is properly positioned on a tissue site, the detector only receives LED emitted light that has propagated through the tissue site after tissue scattering and absorption. Thus, a tissue profile 200 should reflect the blood constituent absorption characteristics illustrated in FIG. 1, above. For this high oxygen saturation (97%) example, HbO2 is the only significantly absorbing blood constituent and, indeed, the resulting tissue profile 200 is shaped like the HbO2 absorption curve 110 (FIG. 1).
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • [0010]
    FIG. 1 is a graph of oxyhemoglobin and reduced hemoglobin light absorption versus wavelength across portions of the red and IR spectrum;
  • [0011]
    FIG. 2 is a graph of NP ratios versus wavelength illustrating a tissue profile;
  • [0012]
    FIG. 3 is a graph of NP ratios versus wavelength illustrating a probe-off profile;
  • [0013]
    FIG. 4 is a graph of NP ratios versus wavelength illustrating a penumbra profile;
  • [0014]
    FIG. 5 is a general block diagram of a confidence measurement system;
  • [0015]
    FIG. 6 is a graph of normalized plethysmograph (NP) ratios versus wavelength for low and high SpO2 illustrating a NP envelope;
  • [0016]
    FIG. 7 is a block diagram of a multiple wavelength probe off detector utilizing an NP envelope;
  • [0017]
    FIG. 8 is a graph of NP ratios versus wavelength illustrating a family of parametric NP curves;
  • [0018]
    FIG. 9 is a block diagram of a multiple wavelength confidence measurement system utilizing parametric NP curves;
  • [0019]
    FIG. 10 is an NP ratio graph illustrating a family of NP data clusters; and
  • [0020]
    FIG. 11 is a block diagram of a multiple wavelength confidence measurement system utilizing NP data clusters.
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
  • [0021]
    In this application, reference is made to many blood parameters. Some references that have common shorthand designations are referenced through such shorthand designations. For example, as used herein, HbCO designates carboxyhemoglobin, HbMet designates methemoglobin, and Hbt designates total hemoglobin. Other shorthand designations such as COHb, MetHb, and tHb are also common in the art for these same constituents. These constituents are generally reported in terms of a percentage, often referred to as saturation, relative concentration or fractional saturation. Total hemoglobin is generally reported as a concentration in g/dL. The use of the particular shorthand designators presented in this application does not restrict the term to any particular manner in which the designated constituent is reported.
  • [0022]
    FIG. 3 illustrates an example of a probe-off profile 300. When a sensor is completely dislodged from a patient, a so-called “probe off” condition occurs. Despite a probe off condition, an optical sensor may continue to detect an AC signal, which can be induced at the detector by other than pulsatile arterial absorption of LED emitted light. For example, small patient movements, vibrations, air flow or other perturbations may cause the pathlength between the LEDs and the detector to vary, resulting in an AC detector signal that can be mistakenly interpreted by the monitor as due to pulsatile arterial blood. Further, ambient light may reach the detector, and any modulation of the ambient light due to AC power, power fluctuations, moving objects, such as a fan, among other perturbations can be also mistaken as a pulsatile arterial signal. Probe off errors are serious because a blood constituent monitor may display normal results, such as oxygen saturation, when, in fact, the sensor is not properly attached to the patient, potentially leading to missed severe desaturation events. As shown in FIG. 3, a probe-off profile 300 is readily apparent as it does not have a shape related to the absorption characteristics of hemoglobin constituents.
  • [0023]
    FIG. 4 illustrates an example of a penumbra profile 400. When a sensor is not properly positioned or becomes partially dislodged, a penumbra condition may occur, where the detector is “shadowed” by a tissue site, such as a finger, but also receives some light directly from the emitters or indirectly reflected off the sensor housing, or both. As a result, the DC signal at the detector rises significantly, which lowers the AC/DC ratio (NP). Because red wavelengths are more significantly absorbed by Hb and HbO2, the penumbra condition is most noticeable at the red portion 405 of the NPλn/ NPλr. This effect is readily seen in the penumbra profile 400 as compared to a normal tissue profile 200 (FIG. 2).
  • [0024]
    Advantageously, a physiological parameter confidence measurement system, as described below, can distinguish a tissue profile 200 (FIG. 2) from a probe-off profile 300 (FIG. 3) or penumbra profile 400 (FIG. 4), as examples. Further, a physiological parameter confidence measurement system can provide indications that the detector signal is degraded as the result of various physiological and non-physiological phenomenon.
  • [0025]
    FIG. 5 illustrates a physiological parameter confidence measurement system 500 having a physiological data 510 input, a confidence indicator 560 output and a probe-off indicator 570 output. In one embodiment, physiological data 510, such as the NP ratios described above, is derived from a sensor 501 generating a sensor signal 502 responsive to multiple wavelengths of optical radiation transmitted into and attenuated by a tissue site. The confidence indicator 560 provides an observer with some measure of “goodness” for the physiological data 510. That is, if confidence is high, it is likely the physiological data 510 is representative of a physiological condition or state. If confidence is low, the physiological data 510 may be less representative of a physiological condition or state. If the confidence is very low, a probe-off indicator 570 may be generated to alert an observer to the possibility that a sensor from which the physiological data 510 is derived is not properly positioned on a tissue site and may not be generating physiologically significant data. In one embodiment, a confidence measure may be provided as a percentage, such as 0-100%. In various embodiments, a confidence indicator 560 corresponding to a confidence measure may be visual or audible or both. For example, a confidence indicator 560 may be a number display, a display message, a bar display, a color indicator or display, such as green (high confidence), yellow (average confidence), red (low confidence). Also, a confidence indicator 560 may be any of various alarm sounds, tones or patterns of sounds or tones, such as a double beep at less than high confidence. In one embodiment, the physiological parameter confidence measurement system 500 is incorporated within a physiological monitor 503 having a display 580 or alarm 590 for outputting the confidence indicator 560 or probe-off indicator 570.
  • [0026]
    As shown in FIG. 5, the physiological parameter confidence measurement system 500 also has a parameter estimator 520, a physiological data reference 540 and a confidence measurer 550. The parameter estimator 520 derives one or more physiological parameter estimates, {circumflex over (P)}, 530 based upon the physiological data 510. The parameter estimate or estimates 530 are used to select one or more data clusters 545 from the physiological data reference 540. In one embodiment, the physiological data reference 540 is a collection of predetermined physiological data organized in data clusters. For example the physiological data reference 540 may contain clinically-derived physiological data organized according to corresponding values of a physiological parameter determined by a “gold standard” instrument. In a particular embodiment, the physiological data are NP ratios obtained for various physiological parameters, such as SpO2, HbCO, HbMet, Hbt, fractional oxygen saturation, bilirubin or glucose to name a few, as measured with a standardized cooximeter, for example. In one embodiment, the physiological data reference 540 is a non-volatile memory or other data storage device containing predetermined physiological data. The confidence measurer 550 uses the physiological data 510 and the selected data cluster or data clusters 545 to generate the confidence indicator 560, the probe-off indicator 570 or both.
  • [0027]
    A confidence measurement and confidence indicator, as described herein, may be combined with other signal quality and data confidence measurements and indicators, such as those described in U.S. Pat. No. 6,996,427 titled Pulse Oximetry Data Confidence Indicator and U.S. Pat. No. 6,606,511 titled Pulse Oximetry Pulse Indicator, both patents assigned to Masimo Corporation, Irvine, Calif. and incorporated by reference herein. A probe off measurement and probe off indicator as described herein may be combined with other probe off measurements and indicators, such as those described in U.S. Pat. No. 6,654,624 titled Pulse Oximeter Probe-Off Detector and U.S. Pat. No. 6,771,994 titled Pulse Oximeter Probe-Off Detection System, both patents assigned to Masimo Corporation, Irvine, Calif. and incorporated by reference herein.
  • [0028]
    FIG. 6 illustrates NP ratio versus wavelength curves computed from a multiple wavelength sensor, such as described in the U.S. Patent Application titled Multiple Wavelength Sensor, referenced above. In this example, the sensor emits eight wavelengths (620, 630, 660, 700, 730, 805, 905 and 960 nm). Shown is a low oxygen saturation curve 610, e.g. SpO2=70% and a high oxygen saturation curve 620, e.g. SpO2≈100%. By comparison, a conventional two wavelength pulse oximetry sensor, as described above, results in a single point on a particular curve. Advantageously, the NP ratio curves 610, 620 represent a tissue profile that can be compared to a particular sensor response to determine if a physiologically significant measurement has been made. In one embodiment, the NP ratio curves 610, 620 delineate the boundaries of a physiologically significant NP ratio region 630. Although described above with respect to SpO2, such regions or boundaries can be derived for other physiological parameters such as HbCO, HbMet, Hbt, fractional oxygen saturation, bilirubin or glucose to name a few.
  • [0029]
    FIG. 7 illustrates one embodiment of a physiological parameter confidence measurement system 700 utilizing a NP ratio region such as described with respect to FIG. 6, above. The confidence measurement system 700 has input NP ratios 710 measured in response to a multiple wavelength sensor, reference NP ratio region 740 that delineates physiologically significant NP ratios 630 (FIG. 6), and a comparator 750. In one particular embodiment, the NP ratio region 740 is predetermined from clinically-derived data for one or more parameters of interest, such as SpO2, HbCO, HbMet, Hbt, fractional oxygen saturation, bilirubin or glucose, to name a few. In another particular embodiment, the NP ratio region 740 is theoretically calculated. The comparator 750 compares the input NP ratios 710 with the NP ratio region 740 and generates a probe-off indicator 770 if any, or more than a predetermine number, of the input NP ratios 710 fall outside of an NP ratio region 740.
  • [0030]
    FIG. 8 illustrates a family of parametric NP ratio versus wavelength curves 800 computed from a multiple wavelength sensor, such as referenced above. Each curve represents a different value of a measured parameter, such as SpO2. For example, there may be a curve for each of SpO2=70%, 75%, 80%, . . . 100%. Advantageously, such curves more precisely indicate physiologically significant multiple wavelength sensor measurements as compared to a bounded NP ratio region 630 (FIG. 6) such as described with respect to FIGS. 6-7, above.
  • [0031]
    FIG. 9 illustrates another embodiment of a physiological parameter confidence measurement system 900 utilizing parametric NP ratio curves, such as described with respect to FIG. 8, above. The confidence measurement system 900 has input NP ratios 910 measured in response to a multiple wavelength sensor, a parameter estimator 920, reference parametric curves 940 and a difference calculator 950. The parameter estimator 920 inputs the NP ratios 910 so as to generate a parameter estimate 930, such as SpO2, HbCO, HbMet, Hbt, fractional oxygen saturation, bilirubin or glucose, to name a few. The estimated parameter 930 selects one or more of the reference parametric curves 940, which are predetermined from clinically-derived data that is stored in memory or data that is mathematically pre-calculated or calculated in real time and stored in memory. The difference calculator 950 measures the difference between the NP ratios 910 and the selected parametric curve 940. For example, a mean-squared error calculation can be made between the input NP ratios 910 and the selected parametric curve 945. The resulting difference calculation is used as a confidence measure or translated into a confidence measure and a confidence indicator output 960 is generated accordingly. Alternatively, or in addition to a confidence measure, a probe off condition can be indicated if the difference calculation is larger than a predetermined value or the confidence measure is less than a predetermined value. In another embodiment, a correlation calculator is used in place of the difference calculation.
  • [0032]
    FIG. 10 illustrates a family of data clusters 1000 shown in two dimensions by way of example. Each data cluster 1000 represents NP ratios clinically measured across a population for specific values 1020 of a selected parameter P. such as P1, P2, P3 and P4 as shown. Each data cluster 1000 defines a region 1010 of NP ratios measured for a particular parameter value 1020 and has a probability distribution, such as a normal distribution, over the indicated region 1010.
  • [0033]
    For example, the clinical data can be organized as a table of known values of P, corresponding NP ratios measured over a population, and the relative number of occurrences of particular NP ratio values for each value of P. The relative number of occurrences of particular NP ratio values for a particular value of P yields an NP ratio probability distribution for that value of P. Thus, each P value 1020 in the table has a corresponding data cluster 1000 of measured NP ratios and an associated probability distribution for those NP ratios.
  • [0034]
    FIG. 11 illustrates yet another embodiment of a physiological parameter confidence measurement system 1100 utilizing NP data clusters and corresponding probability distributions, such as described with respect to FIG. 10, above. The confidence measurement system 1100 has input NP ratios 1110 measured in response to a multiple wavelength sensor, a parameter estimator 1120, reference data clusters 1140 and a probability calculator 1150. The parameter estimator 1120 inputs the NP ratios 1110 so as to generate a parameter estimate 1130, such as described with respect to other embodiments, above. In one embodiment, the reference data clusters 1140, such as described with respect to FIG. 10, are stored in a memory device, such as an EPROM. The estimated parameter 1130 is compared with the reference data clusters 1140 so as to determine the closest region 1010 (FIG. 10) or closest overlapping portion of two regions 1010 (FIG. 10). The probability calculator 1150 computes a probability based upon the distribution above the selected region 1010 (FIG. 10). A confidence measure is also derived based upon the calculated probability 1150. In a particular embodiment, the confidence measure is the calculated probability. A confidence indicator 1160 is generated in response to the confidence measure. In one embodiment, if the confidence probability or the calculated confidence measure is below a predetermined threshold, a probe-off indicator 1170 is generated. In particular embodiments, the confidence indicator 1160 or probe-off indicator 1170 or both may be alphanumeric or digital displays, optical indicators or alarms or similar audible indicators, to name a few.
  • [0035]
    A physiological parameter confidence measurement system has been disclosed in detail in connection with various embodiments. These embodiments are disclosed by way of examples only and are not to limit the scope of the claims that follow. One of ordinary skill in art will appreciate many variations and modifications.
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4907876 *May 2, 1988Mar 13, 1990Hamamatsu Photonics Kabushiki KaishaExamination apparatus for measuring oxygenation in body organs
US4986665 *Aug 3, 1988Jan 22, 1991Minolta Camera Kabushiki KaishaOptical density detector
US5058588 *Sep 19, 1989Oct 22, 1991Hewlett-Packard CompanyOximeter and medical sensor therefor
US5259381 *Jul 10, 1989Nov 9, 1993Physio-Control CorporationApparatus for the automatic calibration of signals employed in oximetry
US5331549 *Jul 30, 1992Jul 19, 1994Crawford Jr John MMedical monitor system
US5645059 *Dec 17, 1993Jul 8, 1997Nellcor IncorporatedMedical sensor with modulated encoding scheme
US5800348 *Sep 23, 1996Sep 1, 1998Hewlett-Packard CompanyApparatus and method for medical monitoring, in particular pulse oximeter
US6122042 *Jul 1, 1997Sep 19, 2000Wunderman; IrwinDevices and methods for optically identifying characteristics of material objects
US6184521 *Jan 6, 1998Feb 6, 2001Masimo CorporationPhotodiode detector with integrated noise shielding
US6253097 *Mar 6, 1996Jun 26, 2001Datex-Ohmeda, Inc.Noninvasive medical monitoring instrument using surface emitting laser devices
US6285895 *Aug 18, 1998Sep 4, 2001Instrumentarium Corp.Measuring sensor for monitoring characteristics of a living tissue
US6611698 *Oct 7, 1999Aug 26, 2003Hitachi, Ltd.Optical measuring instrument
US6743172 *Nov 3, 2000Jun 1, 2004Alliance Pharmaceutical Corp.System and method for displaying medical process diagrams
US20010044700 *Nov 30, 2000Nov 22, 2001Naoki KobayashiApparatus for determining concentrations of hemoglobins
US20010045532 *Jan 25, 2001Nov 29, 2001Schulz Christian E.Shielded optical probe having an electrical connector
US20020021269 *Aug 7, 2001Feb 21, 2002Rast Rodger H.System and method of driving an array of optical elements
US20020038081 *Aug 30, 2001Mar 28, 2002Fein Michael E.Oximeter sensor with digital memory recording sensor data
US20020156353 *Apr 20, 2001Oct 24, 2002Larson Eric RussellPulse oximetry sensor with improved appendage cushion
US20020161291 *Feb 12, 2002Oct 31, 2002Kianl Massi E.Pulse oximeter user interface
US20020183819 *Apr 23, 2001Dec 5, 2002Struble Chester L.Bi-atrial and/or bi-ventricular patient safety cable and methods regarding same
US20040034898 *Aug 26, 2002Feb 26, 2004Bayerische Motoren Werke AgSelf-tinting helmet visor and method of making same
US20040059209 *Sep 22, 2003Mar 25, 2004Ammar Al-AliStereo pulse oximeter
US20040081621 *Jan 17, 2003Apr 29, 2004Frank ArndtOptical imaging method, and an apparatus for optical imaging
US20040133087 *Dec 18, 2003Jul 8, 2004Ali Ammar AlPulse oximetry data confidence indicator
US20040147823 *Jul 22, 2003Jul 29, 2004Kiani Massi EPulse oximetry sensor adaptor
US20040158134 *Nov 25, 2003Aug 12, 2004Diab Mohamed K.Pulse oximeter probe-off detector
US20040262046 *Nov 27, 2002Dec 30, 2004Benedicte SimondApparatus for measuring a biological parameter equipped with a graphic representation display
US20040267103 *Oct 22, 2002Dec 30, 2004Luya LiPhysiological parameter monitoring system and sensor assembly for same
US20050011488 *Jul 19, 2004Jan 20, 2005Rejean DoucetFlow guiding structure for an internal combustion engine
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US8050728Mar 1, 2006Nov 1, 2011Masimo Laboratories, Inc.Multiple wavelength sensor drivers
US8126525 *Dec 1, 2006Feb 28, 2012Ge Healthcare Finland OyProbe and a method for use with a probe
US8130105Mar 1, 2006Mar 6, 2012Masimo Laboratories, Inc.Noninvasive multi-parameter patient monitor
US8190223Mar 1, 2006May 29, 2012Masimo Laboratories, Inc.Noninvasive multi-parameter patient monitor
US8224411Mar 1, 2006Jul 17, 2012Masimo Laboratories, Inc.Noninvasive multi-parameter patient monitor
US8255027Jul 19, 2010Aug 28, 2012Cercacor Laboratories, Inc.Multiple wavelength sensor substrate
US8265723 *Sep 11, 2012Cercacor Laboratories, Inc.Oximeter probe off indicator defining probe off space
US8265724Mar 9, 2007Sep 11, 2012Nellcor Puritan Bennett LlcCancellation of light shunting
US8280469 *Mar 9, 2007Oct 2, 2012Nellcor Puritan Bennett LlcMethod for detection of aberrant tissue spectra
US8301217Oct 30, 2012Cercacor Laboratories, Inc.Multiple wavelength sensor emitters
US8346328Jan 1, 2013Covidien LpMedical sensor and technique for using the same
US8352004Jan 8, 2013Covidien LpMedical sensor and technique for using the same
US8364224Jan 29, 2013Covidien LpSystem and method for facilitating sensor and monitor communication
US8374665 *Feb 12, 2013Cercacor Laboratories, Inc.Tissue profile wellness monitor
US8385996Apr 13, 2009Feb 26, 2013Cercacor Laboratories, Inc.Multiple wavelength sensor emitters
US8391941Jul 17, 2009Mar 5, 2013Covidien LpSystem and method for memory switching for multiple configuration medical sensor
US8417310Apr 9, 2013Covidien LpDigital switching in multi-site sensor
US8483787Oct 31, 2011Jul 9, 2013Cercacor Laboratories, Inc.Multiple wavelength sensor drivers
US8581732Mar 5, 2012Nov 12, 2013Carcacor Laboratories, Inc.Noninvasive multi-parameter patient monitor
US8626255May 22, 2012Jan 7, 2014Cercacor Laboratories, Inc.Noninvasive multi-parameter patient monitor
US8634889May 18, 2010Jan 21, 2014Cercacor Laboratories, Inc.Configurable physiological measurement system
US8718735Jun 3, 2011May 6, 2014Cercacor Laboratories, Inc.Physiological parameter confidence measure
US8781544Mar 26, 2008Jul 15, 2014Cercacor Laboratories, Inc.Multiple wavelength optical sensor
US8801613Dec 3, 2010Aug 12, 2014Masimo CorporationCalibration for multi-stage physiological monitors
US8849365Feb 25, 2013Sep 30, 2014Cercacor Laboratories, Inc.Multiple wavelength sensor emitters
US8912909Nov 11, 2013Dec 16, 2014Cercacor Laboratories, Inc.Noninvasive multi-parameter patient monitor
US8923944Aug 20, 2012Dec 30, 2014Covidien LpCancellation of light shunting
US8929964Jul 8, 2013Jan 6, 2015Cercacor Laboratories, Inc.Multiple wavelength sensor drivers
US8965471Feb 11, 2013Feb 24, 2015Cercacor Laboratories, Inc.Tissue profile wellness monitor
US9066660Sep 29, 2009Jun 30, 2015Nellcor Puritan Bennett IrelandSystems and methods for high-pass filtering a photoplethysmograph signal
US9131882Oct 11, 2013Sep 15, 2015Cercacor Laboratories, Inc.Noninvasive multi-parameter patient monitor
US9167995Mar 18, 2014Oct 27, 2015Cercacor Laboratories, Inc.Physiological parameter confidence measure
US9220440Sep 21, 2009Dec 29, 2015Nellcor Puritan Bennett IrelandDetermining a characteristic respiration rate
US9241662Dec 11, 2013Jan 26, 2016Cercacor Laboratories, Inc.Configurable physiological measurement system
US9326690 *Oct 14, 2008May 3, 2016Shenzhen Mindray Bio-Medical Electronics Co. Ltd.Patient monitor with visual reliability indicator
US9351675Dec 2, 2014May 31, 2016Cercacor Laboratories, Inc.Noninvasive multi-parameter patient monitor
US20070129616 *Dec 1, 2006Jun 7, 2007Borje RantalaProbe and a method for use with a probe
US20080262325 *Apr 21, 2008Oct 23, 2008Marcelo LamegoTissue profile wellness monitor
US20090163787 *Dec 21, 2007Jun 25, 2009Nellcor Puritan Bennett LlcMedical sensor and technique for using the same
US20100094096 *Oct 14, 2008Apr 15, 2010Petruzzelli JoePatient monitor with visual reliability indicator
US20130006076 *Sep 11, 2012Jan 3, 2013Mchale Ryan TimothyOximeter probe off indicator defining probe off space
DE102012212806A1Jul 20, 2012Jan 24, 2013Cercacor Laboratories, Inc.Wiederverwendbarer magnetischer Sensor
DE112011100761T5Feb 28, 2011Jan 3, 2013Masimo CorporationAdaptives Alarmsystem
WO2011109312A2Feb 28, 2011Sep 9, 2011Masimo CorporationAdaptive alarm system
WO2012075322A2Dec 1, 2011Jun 7, 2012Masimo Laboratories, Inc.Handheld processing device including medical applications for minimally and non invasive glucose measurements
WO2013103885A1Jan 4, 2013Jul 11, 2013Masimo CorporationAutomated critical congenital heart defect screening and detection
WO2013148605A1Mar 25, 2013Oct 3, 2013Masimo CorporationPhysiological monitor touchscreen interface
WO2014149781A1Mar 5, 2014Sep 25, 2014Cercacor Laboratories, Inc.Cloud-based physiological monitoring system
WO2014158820A1Mar 4, 2014Oct 2, 2014Cercacor Laboratories, Inc.Patient monitor as a minimally invasive glucometer
WO2015054166A1Oct 6, 2014Apr 16, 2015Masimo CorporationRegional oximetry pod
WO2016057553A1Oct 6, 2015Apr 14, 2016Masimo CorporationModular physiological sensors
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